Compression of digital video data is needed for many applications. Transmission over limited bandwidth channels such as direct broadcast satellite (DBS) and storage on optical media (i.e., DVD, CD, etc.) are typical examples of compressed data. In order to achieve efficient compression, complex computationally intensive processes are used for encoding (or compressing) and decoding (or decompressing) digital video signals. For example, even though MPEG-2 is known as a very efficient method for compressing video, more efficient compression standards such as H.264 are being developed. See, for example, document JVT-E022d7 titled “Editor's Proposed Draft Text Modifications for Joint Video Specification (IUT-T Rec. H.264 ISO/IEC 14496-10 AVC), Draft 7” published Sep. 19, 2002 by the Joint Video Team (JVT) of ISO/IEC MPEG and ITU-T VCEG, Berlin, Germany, which is hereby incorporated by reference in its entirety.
Referring to FIG. 1, a conventional coding/decoding system 10 is shown. The system 10 comprises an encoder 12 and a decoder 14. The encoder 12 comprises an analog to digital converter 20, a scaler 22 and a compression circuit 24. The decoder 14 comprises a decompression circuit 30, a scaler circuit 32 and a digital to analog converter circuit 34.
The encoder 12 scales an entire image before compression. The decoder 14 scales the image after decompression. For example, the A/D converter 20 generates an image having 720×480 pixels (e.g., in International Radio Consultative Committee (CCIR) format). The encoder 12 scales the image horizontally to 544×480 pixels (i.e., a factor of about 75%). The decoder 14 receives the image and rescales to 720×480 pixels before generating a video signal via the converter 34. In another example, the encoder 12 also scales the image to 544×480, but the decoder 14 scales the image to 1920×1080 pixels before the D/A conversion to display the image on a high definition (HDTV) monitor (not shown).
Another apparatus, disclosed in U.S. Pat. No. 6,463,102, modifies one or more edges of an image prior to encoding to make the encoding more efficient. An edge processor alters the image by converting some of the pixels at the image edges to black, blurring the image edges, and/or copying rows or columns of pixels multiple times on the image edges. Through the edge processing, the modified image retains the same size as the original image. The apparatus then encodes and transmits the modified image.
It would be desirable to provide a method and/or apparatus for improving encoding/decoding efficiency by not encoding/decoding an overscan portion from an encode/decode bit-stream.